Wednesday, January 28, 2009

Attachment: The virus attaches to the host cellEntry: The virus injects its DNA into the host cellReplication: The virus directs the replication of its own DNAAssembly: The new phages are assembledRelease: The host cell bursts, releasing the new viruses. Thesenew viruses then spread to other host cells. (Note:the host cell is killed in the process)

Attachment: The virus attaches to the host cellEntry: The virus injects its DNA into the host cellReplication: The virus' DNA combines with the host cell's DNAand both are replicated togetherAssembly: When the host cell reproduces, it also reproduces thevirus' DNA and is packaged into new host cells (Thehost cell is not killed in the process)

Note: After the lysogenic cycle, the cell MAY undergo the lyticcycle, but it doesn't have to.

Retroviruses are RNA viruses that use the enzyme reverse transcriptase to transcribe DNA from an RNA template. The new DNA then integrates into a chromosome in the nucleus of an animal cell, and the host transcribes the viral DNA into RNA. HIV is a retrovirus

Here is a website that has videos, pictures, and information on HIV/AIDS: http://www.boehringer-ingelheim.com/hiv/art/art_videos.htm

Multiple Choice:

1. What is the function of reverse transcriptase in retroviruses?a. It uses viral RNA as a template for making complementary RNAstrandsb. It hydrolyzes the host cell's DNAc. It uses viral RNA as a template for DNA synthesisd. It converts host cell RNA into viral DNAe. It translates viral RNA into proteins

2. HIV, the virus that causes AIDS, only infects certain cells within the immune system. This is becausea. the virus is not very mobile within the body and only comes into contact with a limited number of immune cellsb. other cells produce toxins that destroy the virus before infection can take placec. the virus binds to specific receptors that are only present on certain immune cellsd. the virus gets into all cells, but the viral RNA is immediately destroyed in all but a small number of immune system cellse.infection requires the presence of a specific DNA sequence that is only present in the genome of certain immune system cells3. When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?a. the entire virusb. only nucleic acidc. protein capsid and enclosed nucleic acidd. tail fiberse. only protein capsid

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